[Bug target/27627] __builtin_nanf("") doesn't return a _quiet_ nan on parisc

["gdr at cs dot tamu dot edu" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #8 from gdr at cs dot tamu dot edu  2006-05-23 21:58 -------
Subject: Re:  __builtin_nanf("") doesn't return a _quiet_ nan on parisc

"dave at hiauly1 dot hia dot nrc dot ca" <gcc-bugzilla@gcc.gnu.org> writes:

| ------- Comment #7 from dave at hiauly1 dot hia dot nrc dot ca  2006-05-23
16:28 -------
| Subject: Re:  __builtin_nanf("") doesn't return a _quiet_ nan on parisc
| 
| > ------- Comment #6 from rth at gcc dot gnu dot org  2006-05-23 15:00
-------
| > (In reply to comment #4)
| > > This isn't a target bug as far as I can tell.  The value generated
| > > by __builtin_nanf("") as shown by Nan2.c is 0x7fc00000.  The same
| > > value is printed on x86.  This is a signaling NaN.  Positive quiet
| > > NaNs range between 0x7f800001 and 0x7fbfffff.
| > 
| > Incorrect.  The canonical QNaN on x86 (and most other targets) is
| > 0x7fc00000.  It would seem that PA has the same reversed quiet bit
| > as MIPS.  See real_format->qnan_msb_set and mips_ieee_single.
| 
| Interesting.  The HP architecture docments for PA 1.1 and 2.0
| state that PA-RISC fully conforms to ANSI/IEEE Std 754-1985, so
| I presume that this isn't specified (don't have a copy of the
| spec handy), so there's no actual canonical format.  I see this
| was something of a point of contention in 754R meetings.

The IEEE--754 specification is a *conceptual model*, not a "physical"
wired format.  As long as the units behave functionally as required,
it should be fine.

-- Gaby


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27627